The purpose of the proposed research is to gain quantitative information concerning the neuronal basis of somatic sensibility. The specific objective is to understand the organization of the central nervous system and interactions with specific skin receptor systems in relation to encoding and processing of somaesthetic information. In particular, the goal is to determine how various central neuronal networks process temporally-dispersed activity produced by natural stimulation of specific skin receptors; to reveal the central organizational consequences of the heterogeneity of skin receptor systems; to evaluate the relative importance of the variety of synaptic mechanisms associated with central integrative processing of non- synchronous patterned activity from the periphery; and, to assess the special capacities of various ascending spinal systems for information storage and processing. The methodology, which relies heavily on online computer averaging, is now sufficiently refined to enable selective quantitative stimulation of specific skin receptors. Interactions among central neurons will be studied using multiple single unit recording, impulse sorting and analysis of correlated activity.